This invention relates to metal complexes and to addition polymerization catalysts formed therefrom that have improved catalytic performance. More particularly the present invention relates to an addition polymerization catalyst composition comprising a Group 4 metal complex containing a saturated tricyclic ligand group. In addition, the present invention relates to catalyst compositions comprising the foregoing complexes. Finally, the invention relates to a method of using the foregoing catalyst compositions in an addition polymerization process for polymerizing addition polymerizable monomers.
In U.S. Pat. No. 5,455,317 and U.S. Pat. No. 5,416,228 there are disclosed certain bis-cyclopentadienyl metal complexes in which one cyclopentadienyl ligand contains a bulky group in one and only one distal position. The cyclopentadienyl ligand groups are desirably sterically different. The references further disclose complexes wherein the remaining cyclopentadienyl group has bilateral or pseudobilateral symmetry. Such metal complexes are useful in combination with activating cocatalysts as olefin polymerization catalysts, especially in the preparation of polymers of C.sub.3 and higher .alpha.-olefins that are highly isotactic. For the teachings contained therein, the foregoing United States patents and applications are herein incorporated by reference.
It would be desirable if there were provided improved metal complexes and improved catalyst compositions derived therefrom as well as an improved addition polymerization process utilizing such catalyst compositions.